Hydrogels are formed by creating bridges between and within polymer chains through the attachment of small bridging molecules to the functional moieties of the polymer backbone, a process known as cross-linking. The structural integrity of conventional hydrogels is based upon the covalent chemistry used for the cross-linking, which typically requires catalysts to facilitate the reactions in a timely fashion. The presence of catalysts impedes the medical use of hydrogels, especially in surgical applications, because they are potentially injurious to surrounding tissues. Thus, there is a need for hydrogels that can be polymerized rapidly without the use of chemical cross-linking catalysts.